The present invention relates to a method and apparatus for washing or hydration of ophthalmic devices.
The molding of hydrophilic contact lenses is known. Various processes are disclosed in U.S. Pat. No. 4,495,313, to Larsen; U.S. Pat. No. 4,640,489 to Larsen, et al.; U.S. Pat. No. 4,680,336 to Larsen et al.; U.S. Pat. No. 4,889,664 to Larsen et al.; and U.S. Pat. No. 5,039,459 to Larsen et al., all of which are assigned to the assignee of the present invention.
These prior art references disclose a contact lens production process wherein each lens is formed by molding a reactive mixture in a lens mold, typically between a front curve (lower mold section) and back curve (upper mold section). The monomer injected in the molds is polymerized, thus forming a lens. The lens is typically subjected to a hydration bath, and then to multiple leaching steps which remove processing chemicals (leachable diluents and monomers) from the lens. Multiple lenses are immersed in the hydration bath, which removes the lenses from the front curve mold. Once demolded, the lenses are advanced into a multi-step washing phase and then the lenses, while still wet, are removed from the washing phase and are packaged for consumer use.
In the earlier manufacturing processes for making contact lenses, the steps of hydration and diluent removal took place in large tanks. Hundreds of contact lenses were put in each tank and moved around the tank and then removed. By in-flow and out-flow streams, the tanks would be kept at a specified equilibrium level of diluent. There were several tanks with decreasing levels of diluent in which the contact lenses were soaked in sequence until they reached the equilibrium level of diluent. The contact lenses would be moved from one tank to the next until the level of diluent was below or at an acceptable level. Occasionally the tanks would be emptied for cleaning, and then refilled with clean water.
U.S. Pat. Nos. 5,080,839 and 5,094,609 disclose, respectively, a process for hydrating and washing contact lenses and a chamber for washing the contact lenses formed with a monomer or monomer mixtures of the type disclosed in the foregoing patents. The process disclosed in these patents was a significant advance; however, the transfer of lenses from the hydration phase to the washing step and the associated handling of the lenses resulted in the loss of some lenses. Plus, washing required large amounts of water and occurred in multiple soaking steps. The chamber holding the contact lens was filled with water, then after the contact lens and H2O reached equilibrium, the chamber was emptied and the steps were repeated.
As should be apparent, it would be desirable to make the hydration step more efficient, that is, to subject as many lenses as possible to hydration in the most efficient manner, using the least water possible.
In accordance with the invention, a hydration and/or washing, e.g. diluent removal, apparatus and process is disclosed in which a plurality of device-supporting members are provided preferably having one or more cavities each for containing an ophthalmic device, such as a contact lens and/or lens mold and/or reusable lens mold, and/or intraocular lens. The ophthalmic devices are arranged so that the hydration or cleansing fluid flows or is directed from contacting cleaner ophthalmic devices to contacting dirtier ophthalmic devices. The device-supporting members can be arranged in any configuration so that the hydration or cleansing fluid contacts cleaner and then dirtier ophthalmic devices. The device-supporting members can be arranged vertically: in-line like a column or like a stair-case, horizontally, helically or combinations of the above. For example, the fluid could flow horizontally from ophthalmic device to ophthalmic device on a first level of one or more device-supporting members arranged is horizontally and then flow vertically down and across to a second level of one or more device-supporting members located beneath the first level, and then flow to a third level, etc. Alternatively, ophthalmic devices can be moved within a column in which the water falls like rain, or in a horizontal pipe through which a stream of fluid is pumped. Preferably the arrangement is at least partially vertical so that the hydration or cleansing fluid moves under gravity and does not have to be pumped. The hydration or cleansing fluid can be directed to move in a single stream from the cleanest ophthalmic device to the dirtiest ophthalmic device in the apparatus. Alternatively, the fluid can be directed to move in multiple streams from one or more of the cleanest ophthalmic devices to one or more of the dirtiest ophthalmic devices in the apparatus. The flow of fluid can be across ophthalmic devices and device-supporting members or it can be through or both across and through the device-supporting members. Preferably, multiple streams of the hydration or cleansing fluid can be directed to flow onto and across only ophthalmic devices in particular locations from clean to dirty ophthalmic devices in the apparatus. Preferably, the fluid flows across the device-supporting members. If desired, additional fluid can be injected at one or more locations in the apparatus. The cleanest ophthalmic devices from the apparatus are removed at or near, that is in the vicinity of the input of clean hydration or cleansing fluid into the apparatus, and dirty ophthalmic devices are inserted into the apparatus preferably just before or in the vicinity of where the dirtiest hydration or cleansing fluid exits the apparatus.
The preferred hydration and/or washing apparatus and process comprises trays as the device-supporting members. However, the device-supporting members can have any configuration, which provides protection for and maintains the ophthalmic device but allows fluid to flow to, and around or over the ophthalmic device in or on the device-supporting member, and then allows the fluid to flow out of the device-supporting member. Other examples of device-supporting members include a plastic cage, bowl, or the hydration and washing chambers for contact lenses used and disclosed in the prior art. It is further preferred that the device-supporting member can be easily moved through the apparatus countercurrent to the flow of the fluid. In the preferred embodiment, the device-supporting member is a lens supporting member, and the preferred lens supporting member is a tray. The preferred- trays have a plurality of cavities each for containing an ophthalmic device, and preferably for containing a front curve mold with a contact lens in the mold. The following description will focus on the preferred embodiment involving the washing and hydration of contact lenses; however, other devices, particularly other ophthalmic devices may be substituted for the contact lenses in the description.
In the preferred embodiment, the trays are stacked vertically with the cavities (and lenses) in columns. The hydration or cleansing fluid, for example, de-ionized (DI) water, is injected or otherwise introduced into each of the cavities of the leading or upper tray. The fluid injected in each cavity flows downwardly through the stack of cavities of the column to wash over the lenses preferably in the front curve molds in the trays below the point where the fluid is injected. If desired, additional fluid also can be injected at one or more lower trays in the stack. In using the apparatus, a tray is inserted at the stack bottom, the stack is raised, and the uppermost tray in the stack is removed. The addition and removal of trays to the stack is carried out in a step-wise manner.
As lenses (in the trays) move upwardly in the stack, they encounter increasingly purer (less contaminated) hydration or cleansing fluid. The more contaminated fluid contacts the is lenses at lower positions in the stack, but is still able to remove contaminants.
There is a counter-current effect, that is, the fluid flows downwardly in the apparatus and the trays with lenses move progressively upward. A vertical configuration is preferred, because the fluid flows down; however, other configurations, including horizontal, in which the fluid is pumped can be used. As the fluid flows from cleaner to dirtier lenses, it picks up the impurities from the lenses. As the lenses move toward the inlet of clean fluid, they have fewer impurities. Preferably, the concentration of impurities in the fluid is always less than the concentration of impurities in the lenses which it is contacting.
According to one aspect of the invention, a method for hydrating or washing ophthalmic devices includes the steps of applying to an ophthalmic device, which has a higher concentration of impurities, a fluid which has previously been applied to ophthalmic devices having a lower concentration of impurities, said fluid having previously been applied to ophthalmic devices having an even lower concentration of impurities. At least a portion of the same fluid preferably is applied to at least 10, more preferably at least 25 ophthalmic devices, most preferably more than 35, e.g. contact lenses, which have substantially sequentially increasing amounts of impurities. For example, lenses having high concentrations of impurities can be lenses having greater than 10,000 ppm, or even greater than 100,000 ppm diluent or other impurities in the lens, and lenses having low concentrations of impurities can be lenses having less than 10 ppm, more preferably less than 1 ppm diluent or other impurities in the lens. Preferably the same fluid, or at least a portion of the same fluid, which is applied to contact lenses having a low concentration of impurities is later applied to contact lenses having a high concentration of impurities. Preferably the is contact lenses move countercurrently to the fluid, and/or (preferably and) the fluid moves countercurrently to the lenses. Preferably, the flow of the fluid is directed from lenses having lower concentrations of impurities to lenses having higher concentrations of impurities, such that the amount of impurities in the fluid increases as the fluid is directed at contact lenses having increasing amounts of impurities. It is preferred that the concentration of impurities in the fluid is such that, a concentration gradient between the level of impurities in the fluid and the lenses is substantially maintained, such that impurities substantially continuously or successively, for example, in stages e.g. at the different levels in the stack, move into the fluid from the cleaner contact lenses and then from the contact lenses having increasingly higher levels of impurities. Preferably the impurities move substantially continuously from the contact lenses into the fluid. The contact lenses enter the apparatus of this invention with a high concentration of impurities and are preferably subjected to increasingly cleaner fluid as the contact lenses become increasingly cleaner. The lenses having the lowest concentration of impurities of any lenses contacting any fluid in this method, have clean, preferably the cleanest, fluid directed at them. In the preferred embodiment the lenses move in stages and the fluid flows continuously or semi-continuously, e.g. in pulses of fluid, countercurrently relative to the movement of the lenses; however, the lenses could also move continuously or semi-continuously countercurrently relative to the movement of the fluid, or both. In this method, the lenses are preferably contained in lens supporting members. In the preferred embodiment, the lenses are in trays, with the trays arranged in a vertical stack. Preferably there are multiple lenses in each tray; however, the trays can be made to hold individual lenses. The concentration of impurities in the lenses in the vertically arranged trays decreases as the lenses advance toward the top of the stack. The fluid is clean at the top of the stack and exits at the bottom of the stack with a high concentration of impurities.
In accordance with another aspect of the invention, a hydrating or washing method includes the steps of vertically arranging, e.g. stacking, a plurality of device-supporting members each having at least one a cavity containing an ophthalmic device, and injecting a fluid into the cavity or cavities of an upper device-supporting member, the fluid flowing downwardly through the cavities. In the preferred form, the downward flow of fluid is directed to a lens contained in the cavity of a lower tray in a stack of trays. Also, the trays can be aligned above one another to define a flow path therebetween.
In accordance with another aspect of the invention, a device-supporting member for use in a washing or hydration apparatus is provided which comprises a cavity. The preferred device-supporting member comprises a support and cavity insert, preferably multiple cavity inserts which fit into the support. The benefit of this configuration is that the cavity inserts can be easily replaced in the support if one of them breaks which limits the loss and expense if there is damage to a device-supporting member. Alternatively, the entire device-supporting member and/or the inserts could be injection molded, which also limits the loss and expense if there is damage to a device-supporting member as compared to a machined plastic or formed metal device-supporting member or cavity insert.
In accordance with another aspect of the invention, an apparatus for hydrating or washing contact lenses includes a means for applying fluid to a lens having a low concentration of impurities, and a means for directing the applied fluid to further lenses which have a comparatively higher concentration of impurities.
According to a still further aspect of the invention, a hydrating or washing apparatus for contact lenses includes a plurality of trays each containing a lens, wherein the trays are vertically stacked, with the cavities arranged in a vertical column. Each cavity has an opening which permits fluid to flow to the cavity of a next lower tray in the stack to thereby wash the lens therein. The apparatus further has an injection passage into which the fluid is injected into the cavity to thereby flow into the opening and to the cavities of lower trays in the vertical column.
Alternatively and more preferably, the apparatus comprises means for intermittently injecting fluid into said apparatus; and means for heating the injecting means to provide a consistent fluid temperature within a pre-determined specified range. In the preferred embodiment a fluid is injected, more preferably via pulses into the uppermost tray onto the ophthalmic device by an extraction head (the injecting means) that comprises a nozzle, which will be described below. Further, the extraction head comprises heating means to insure that the temperature of the fluid to be injected remains constant and does not change between pulses. In the preferred embodiment the heating means is a flow-through extraction head. Maintaining the fluid at a high temperature, preferably close to the highest temperature that the ophthalmic devices can be subjected to without causing damage to the ophthalmic devices provides for increased removal of impurities from the ophthalmic devices as compared to the result if a fluid at a lower temperature is used. The injecting means with heating means is also beneficial for when there are interruptions in the operation of the apparatus due to jams or other maintenance needs in the manufacturing line for ophthalmic devices which requires that the injection of fluid onto ophthalmic devices be temporarily stopped.
Further features and aspects of the invention can be appreciated from the following detailed description and accompanying drawings.
It is an object of the invention to provide a novel method and apparatus for hydration and/or removal of impurities from ophthalmic devices.
A further object is to provide a contact lens hydration and/or washing method and apparatus in which the lenses are stacked vertically in trays which are moved upwardly, and a fluid flows downwardly in the tray stack to successively wash the lenses in the lower trays of the stack. The fluid may be introduced at the top of the stack or fresh fluid or a different fluid composition may be introduced at various points in the process and method.
An additional object is to provide a method and apparatus for efficiently washing ophthalmic devices in an apparatus in which the fluid cascades downwardly over the ophthalmic device.
Yet a further object is to hydrate and wash ophthalmic devices stacked vertically in a column using the same fluid.
Still a further object is to reduce the amount of water consumed during a hydration and/or washing phase.
Yet another object is to increase the rate of diffusion during a hydration and/or washing phase. One method to increase the rate of diffusion is to keep the fluid consistently hot at the injection point.
Still another object is to reduce the amount of lens handling as the lenses are brought to and removed from the hydration phase.